1. Field of the Invention
The present invention relates generally to a communication system, and in particular, to a system and method for notifying completion of a network re-entry procedure in a communication system.
2. Description of the Related Art
In the next generation communication system, active research is being conducted to provide service capable of transmitting/receiving high-speed, high-capacity data to/from mobile stations (MSs). A typical example of the next generation communication system is an Institute of Electrical and Electronics Engineers (IEEE) 802.16e communication system.
Referring to FIG. 1, herein is a description of an MS performing a process of a network re-entry procedure with a target base station (BS) after performing connection switching, e.g., handover, from a serving BS to the target BS in a general IEEE 802.16e communication system.
FIG. 1 is a signaling diagram illustrating a process of performing a network re-entry procedure in a general IEEE 802.16e communication system.
Referring to FIG. 1, following handover from a serving BS to a target BS 150, an MS 100 obtains downlink synchronization with the target BS 150, and receives parameters to be used in an uplink and a downlink, in step 111. Thereafter, the MS 100 should obtain uplink synchronization by performing a ranging operation with the target BS 150, and perform an operation of adjusting transmission power. Therefore, the MS 100 transmits a Ranging Request (RNG-REQ) message to the target BS 150 in step 113, and the target BS 150 transmits a Ranging Response (RNG-RSP) message to the MS 100 in response to the RNG-REQ message in step 115.
Upon performing the ranging operation as described above, the MS 100 transmits a Subscriber Station Basic Capability Request (SBC-REQ) message to the target BS 150 to request the basic capabilities of the target BS 150 and the MS 100 in step 117. The SBC-REQ message, which is a Medium Access Control (MAC) message that the MS 100 transmits to the target BS 150 to request the basic capabilities, includes therein information on a Modulation and Coding Scheme (MCS) level supportable by the MS 100. Upon receipt of the SBC-REQ message from the MS 100, the target BS 150 detects an MCS level supportable by the MS 100, included in the received SBC-REQ message, and transmits a Subscriber Station Basic Capability Response (SBC-RSP) message to the MS 100 in reply to the SBC-REQ message in step 119.
Upon receipt of the SBC-RSP message, the MS 100 transmits a Privacy Key Management Request (PKM-REQ) message to the target BS 150 for MS authentication and key exchange in step 121. The PKM-REQ message, a MAC message for MS authentication, includes a certificate (unique information) of the MS 100. Upon receipt of the PKM-REQ message, the target BS 150 performs authentication with an Authentication Server (AS) (not shown) using the certificate of the MS 100, included in the received PKM-REQ message. If the MS 100 is an authenticated MS as a result of the authentication, the target BS 150 transmits a Privacy Key Management Response (PKM-RSP) message to the MS 100 in response to the PKM-REQ message in step 123. The PKM-RSP message includes an Authentication Key (AK) and a Traffic Encryption Key (TEK) allocated to the MS 100.
Upon receipt of the PKM-RSP message, the MS 100 transmits a Registration Request (REG-REQ) message to the target BS 150 in step 125. The REG-REQ message includes MS registration information for the MS 100. Upon receipt of the REG-REQ message, the target BS 150 detects MS registration information included in the received REG-REQ message, registers the MS 100 therein using the MS registration information, and transmits a Registration Response (REG-RSP) message to the MS 100 in response to the REG-REQ message in step 127. The REG-RSP message includes the registered MS registration information. The MS 100 receives the REG-RSP message, completing its network re-entry procedure to the target BS 150 in step 129. As the MS 100 receives the REG-RSP message, a normal operation is performed between the MS 100 and the target BS 150, completing the network re-entry procedure. The process of performing the network re-entry procedure in the general IEEE 802.16e communication system has been described above with reference to FIG. 1. Next, with reference to FIG. 2, a description will be made of a process of performing a network re-entry procedure based on Handover Process Optimization Type/Length/Value (TLV) in a general IEEE 802.16e communication system.
FIG. 2 is a signaling diagram illustrating a process of performing a network re-entry procedure based on Handover Process Optimization TLV in a general IEEE 802.16e communication system.
Referring to FIG. 2, following handover from a serving BS to a target BS 250, an MS 200 obtains downlink synchronization with the target BS 250, and receives parameters to be used in an uplink and a downlink, in step 211. The MS 200 transmits an RNG-REQ message to the target BS 250 in step 213, and the target BS 250 transmits an RNG-RSP message to the MS 200 in response to the RNG-REQ message in step 215. The RNG-RSP message includes HO Process Optimization TLV, and the HO Process Optimization TLV, an Information Element (IE) included using a TLV encoding scheme, is an IE of a connection switched MS, for example, a handover-processed MS, used for supporting a fast network re-entry procedure with the target BS. That is, the HO Process Optimization TLV is an IE written to make it possible to omit some or all of the message transmission/reception processes that should necessarily be performed in the general network re-entry procedure for the fast network re-entry procedure of the MS 200.
When the MS 200 performs general handover or idle mode handover, the target BS 250 can acquire information on the MS 200 via a backbone network from the system having the information on the MS 200, like the serving BS or a paging controller, before the MS 200 performs the general handover or idle mode handover. The information on the MS 200 can be equal to the information acquired in the process of performing by the MS 200 the network re-entry procedure after its handover from the serving BS to the target BS 250. In this case, by acquiring the information on the MS 200 via the backbone network, the target BS 250 can omit a particular message transmission/reception process in the network re-entry procedure due to the handover of the MS 200, and can not only save the air link resources necessary for the particular message transmission/reception process but also advance a normal communication restart time with the MS 200. Therefore, the target BS 250 includes the HO Process Optimization TLV in order to transmit to the MS 200 a notification indicating the message transmission/reception process omittable in the process of performing the network re-entry procedure. A format of the HO Process Optimization TLV is shown in Table 1 below.
TABLE 1HO ProcessFor each Bit location, a value of ‘0’ indicates theOptimizationassociated re-entry management message shall berequired, a value of ‘1’ indicates the re-entrymanagement messages may be omitted.Bit #0: Omit SBC-REQ management message duringcurrent re-entry processingBit #1: Omit PKM Authentication phase except TEKphase during current re-entry processingBit #2: Omit PKM TEK creation phase during currentre-entry processingBit #3: BS shall transmit an unsolicited SBC-RSPmanagement message with updated capabilitiesinformation in case capabilities of Target BS aredifferent from the ones of Serving BSBit #4: Omit REG-REQ management message duringcurrent re-entry processingBit #5: BS shall transmit an unsolicited REG-RSPmanagement message with updated capabilitiesinformationBit #6: BS supports virtual SDU SN. If Bit#6 = 1 andMS supports SDU SN, it shall issue SN Report headerupon completion of HO to this BS.
In Table 1, the HO Process Optimization TLV is a type of bitmap information indicating whether it is possible to omit transmission/reception of a message in the current network re-entry procedure. That is, the HO Process Optimization TLV IE is expressed in the form of; for example, a 7-bit bitmap. Below is a description of each bit of the HO Process Optimization TLV bitmap.
(1) Whether it is possible to omit transmission of an SBC-REQ message is indicated by a first bit Bit#0. Bit#0=0 indicates that the MS 200 should necessarily transmit the SBC-REQ message, and Bit#0=1 indicates that the MS 200 can omit transmission of the SBC-REQ message.
(2) Whether it is possible to omit a PKM authentication process is indicated by a second bit Bit#1. Bit#1=0 indicates that the MS 200 should perform the PKM authentication process including a TEK process, and Bit#1=1 indicates that the MS 200 can omit the PKM authentication process except for the TEK process.
(3) Whether it is possible to omit the TEK process is indicated by a third bit Bit#2. Bit#2=0 indicates that the MS 200 should necessarily perform the TEK process, and Bit#2=1 indicates that the MS 200 can omit the TEK process.
(4) Whether it is possible to omit transmission of an SBC-RSP message is indicated by a fourth bit Bit#3. Bit#3=0 indicates that the target BS 250 should necessarily transmit an unsolicited SBC-RSP, and Bit#3=1 indicates that the target BS 250 can omit transmission of the SBC-RSP message by transmitting the information included in the SBC-RSP message along with the RNG-RSP message using the TLV encoding scheme.
(5) Whether it is possible to omit transmission of a REG-REQ message is indicated by a fifth bit Bit#4. Bit#4=0 indicates that the MS 200 should necessarily transmit the REG-REQ message, and Bit#4=1 indicates that the MS 200 can omit transmission of the REG-REQ message.
(6) Whether it is possible to omit transmission of a REG-RSP message is indicated by a sixth bit Bit#5. Bit#5=0 indicates that the target BS 250 should necessarily transmit an unsolicited REG-RSP, and Bit#5=1 indicates that the target BS 250 can omit transmission of the REG-RSP message by transmitting the information included in the REG-RSP message along with the RNG-RSP message using the TLV encoding scheme.
(7) Whether the target BS 250 supports a virtual Service Data Unit (SDU) Sequence Number (SN) is indicated by a seventh bit Bit#6. If the Bit#6 is set to ‘1’ and the MS 200 also supports the virtual SDU SN, the MS 200 should transmit an SN Report header to the target BS 250 after completing the network re-entry procedure with the target BS 250.
When Bit#3 and Bit#5 of the HO Processor Optimization TLV included in the RNG-RSP message are both set to ‘1’, the TLV included in the RNG-RSP message is shown in Table 2 below.
TABLE 2If (HO ProcessOptimization [bit#3] == 1)SBC-RSP encodingSBC-RSP TLV items for HO optimizationIf (HO ProcessOptimization [bit#5] == 1)REG-RSP encodingREG-RSP TLV items for HO optimization
In Table 2, if Bit#3 of the HO Process Optimization TLV is set to ‘1’, it indicates SBC-RSP encoding information included in the RNG-RSP message. If Bit#5 of the HO Process Optimization TLV is set to ‘1’, it indicates REG-RSP encoding information included in the RNG-RSP message.
Thereafter, the MS 200 and the target BS 250 perform the network re-entry procedure according to the HO Process Optimization TLV. For example, if the HO Process Optimization TLV bitmap is set to ‘1110100’, the MS 200 omits transmission of an SBC-REQ message in step 217, the target BS 250 transmits an unsolicited SBC-RSP message to the MS 200 in step 219, the MS 200 omits transmission of a PKM-REQ message in step 221, the target BS 250 omits transmission of a PKM-RSP message in step 223, the MS 200 omits transmission of an REG-REQ message in step 225, and finally, the target BS 250 transmits an unsolicited REG-RSP message to the MS 200 in step 227.
As another example, if the HO Process Optimization TLV bitmap is set to ‘1111110’, the target BS 250 should transmit the information included in both the SBC-RSP message and the REG-RSP message along with the TLV of the RNG-RSP message. In this case, the MS 200 and the target BS 250 can normally complete the network re-entry procedure in step 229, even though they omit all the message transmission/reception processes shown in steps 217 to 227.
As described above, in the course of performing the network re-entry procedure, the MS and the target BS can omit some or all of the message transmission/reception processes in the network re-entry procedure according to the HO Process Optimization TLV.
Although the MS fails to normally receive the RNG-RSP message from the target BS, it is impossible for the target BS to recognize the MS's failure to normally receive the RNG-RSP message. In this case, though the target BS performs the network re-entry procedure according to the HO Process Optimization TLV, the MS may perform the general network re-entry procedure, causing mis-synchronization of the message transmission/reception process between the MS and the target BS.
In addition, if the target BS transmits an unsolicited SBC-RSP message or an unsolicited REG-RSP message without a request of the MS, i.e., if the target BS unilaterally transmits the message to the MS without performing the general message transmission/reception process, it is impossible for the target BS to recognize whether the MS has normally received the unsolicited SBC-RSP message or the unsolicited REG-RSP message.
Therefore, there is a need for a scheme in which the target BS can recognize whether the MS has normally received an unsolicited message that the target BS transmitted without the request of the MS, or a message included in the HO Process Optimization TLV, while the MS and the target BS are performing the network re-entry procedure according to the HO Process Optimization TLV.